50 Prof. L. Vegard : Results of Northliglit Investigations 



We notice that, despite the fact that all forms on an 

 average had their lower boundary almost at the same height^ 

 the upper limit shows great difference. The ray-form may 

 reach a height 400 km., while the arcs usually are extin- 

 guished at a height of 150 km. 



The height distributions of the lower limit of the various 

 forms is given in Table III., and graphically represented in 

 fig. 1 (PL II.). 



Table III. 



tt . , Drapery- 



Kays. Draperies. shaped 

 Arcs. 



iotei-vals. 



km. 

 73 

 77 

 79 

 84 



85-87 ... ... 4 



87-89 ... 3 '4 



89-91 ... 8 14 



91-93 ... 8 16 



93-95 1 10 25 



95-97 ... 13 42 



97-99 ... 23 66 



99-101 3 42 113 



101-103 ... 25 65 



103-105 2 34 69 



105-107 2 53 99 



107-109 10 26 70 



109-111 11 21 55 



111-113 5 21 51 



113-115 3 15 50 



115-117 5 15 31 



117-119 5 18 16 



119-121 5 9 16 



121-123 2 10 12 



123-125 1 6 23 



125-127 3 4 9 



127-129 14 6 



129-131 ... 3 6 



131-133 1 2 7 



133-135 ... 4 6 



135-137 1 1 4 



137-139 ... 6 3 



139-141 ... 5 1 



141-143 ... 5 1 



143-145 ... 3 



145-147 .. 2 



147-149 ... 2 3 



149-151 ... 2 



151-153 ... 1 1 



153-155 ... 3 



155-157 ... 1 

 157-159 

 159-161 

 161-163 

 163-165 



Diffuse 



Pulsating 



Total 



Arcs. 



Aurorae. 







1 



1 





1 



1 





1 



1 





1 



1 



1 



1 



6 



4 



2 



13 



7 



3 



32 



6 



2 



32 



7 



6 



49 



21 



11 



87 



15 



12 



116 



32 



13 



203 



15 



15 



120 



33 



13 



151 



51 



14 



219 



35 



10 



151 



35 



8 



130 



27 



6 



110 



18 



7 



93 



18 



5 



74 



14 



5 



58 



15 



2 



47 



12 



6 



42 



8 



3 



41 



5 



6 



27 



5 



2 



18 



6 



2 



17 



4 



1 



15 



3 





13 



1 





7 



4 





13 



4 





10 

 6 

 3 

 2 

 5 



"i 





3 



i 





3 



i 





4 





"l 



2 



165-167 





1 









1 



Sum 



61 



409 



888 



499 



160 



1927 



